An anti-aircraft missile and other weapons have reportedly been found on a suspected North Korean spy ship which sank after a gun battle with the Japanese coast guard last year.

The ship was engaged in a six-hour chase

Reports from Japan said the weapons were spotted by divers during an underwater survey of the ship.

High waves in the East China Seas have forced Japan's coast guard to delay for a second day plans to salvage the vessel.

North Korea's Foreign Ministry has denied having anything to do with the boat.

Sophisticated arsenal

Japanese government sources said a Russian surface-to-air heat-seeking missile, portable anti-tank grenade launchers and machine guns were seen on the ship.

"It is truly terrifying that the mystery ship was so heavily
armed, much more so than we had thought," one Japanese government source told Reuters news agency, on condition of anonymity.

However Japanese officials would not confirm the reports.

"I know it has been reported in the media. But I think it is
based on speculation," Deputy Chief Cabinet Secretary Kosei Ueno told reporters on Wednesday.

North Korean links

Earlier reports quoted Japanese officials as saying that pictures showed the crew of the foreign boat using shoulder-held rocket launchers, similar to Soviet-made weapons that are known to be in North Korea's arsenal.

Japan is conducting an inquiry into the incident

All 15 crew on board are thought to have died and the ship is now lying in 90 metres (295 feet) of water at the bottom of the East China Sea.

The bodies of two of the crew members have been recovered. Both had items with labels in Korean.

The mystery boat sank on 22 December after a six-hour chase and fire fight with Japanese patrol ships.

The vessel, having failed to heed Japanese warning shots and an order to stop, fled in the direction of China before it sank.

It was initially believed to have been sunk by Japanese fire, but Japan has raised the possibility that the crew scuttled the ship.

Salvage operation

The ship sank near Chinese territorial waters, in what Beijing calls its exclusive economic zone, but where Japan claims the right to protect its fishing and mineral resources.

China gave Japan permission last week to raise the ship, provided both countries discussed compensation for what China says is damage caused to its fisheries by Japanese patrols.

The Japanese coast guard says the inquiry is a "criminal investigation" into attempted murder, as the vessel had returned fire after the coast guard fired warning shots.